Powder coating booth containment structure

ABSTRACT

A powder coating booth containment structure including first and second canopy halves, each of which is a substantially nonconductive, seamless, structural composite to substantially reduce oversprayed powder particle adhesion to the booth inner surfaces. The composite canopy halves, when assembled into a spray booth additionally including either a floor or a utility base and one or a pair of end units in the form of aperture bulkheads, vestibules, or a combination of both, are structurally sufficiently strong that no external support frame is required. The composite canopy halves can each include sidewall and ceiling portions, in an embodiment, that can be connected to a floor. In another embodiment, the canopy halves each additionally include a floor portion such that they may be connected together at a floor edge and placed atop a utility base. They may be connected to the utility base. In another embodiment, the canopy halves may each further include an integral end or ends, comprising aperture bulkhead or vestibule-type end portions. Methods of assembling these embodiments are also provided that require less time than for known powder coating spray booth assembly.

FIELD OF THE INVENTION

The present invention relates to powder coating spray booths used forcontaining powder particles that do not adhere to articles intended tobe coated. More specifically, the invention relates to a substantiallynon-conductive spray booth comprising a pair of self-supporting,one-piece, composite, seamless canopy booth halves.

BACKGROUND OF THE INVENTION

Powder spray booths for electrostatic powder coating operations are wellknown and are used for environmental purposes to contain oversprayedpowder coating material that does not adhere to the target article. Inaddition, the booth facilitates collection of the oversprayed powdermaterial which is often recycled back into the application system. In anelectrostatic powder coating operation, the powder particles arecharged, such as by one or more high voltage charging electrodes on anelectrostatic powder spray application device, such as a spray gun, andthe parts are grounded. The difference in potential creates anattraction of the powder particles to the surface of the parts.Typically, such target parts are overhead conveyed through the booth viaone continuous slotted opening extending from one end of the booththrough the ceiling and out the opposite end of the booth. The targetparts are spray-coated therein as they pass at a controlled rate throughthe booth.

A powder coating booth and application system must be completely cleanedand purged of one color of powder coating material prior to a successivecoating operation using a different powder color. Cleaning a powdercoating spray booth can be a labor-intensive effort. In a productionpowder coating environment, minimizing the system down time to changefrom one color of powder coating material to another is a criticalelement in controlling operational costs. Powder material tends to geteverywhere within the spray booth during a powder coating operation.During extended powder coating runs, the amount of oversprayed powderaccumulated within the booth can impact color change time. Seams betweenbooth panels and recessed ledges, such as where access doors orautomatic or manual spray application devices may be located, aretypically hard to clean areas and tend to hold concentrations ofoversprayed powder coating material that could present a contaminationrisk after a color change. In addition to seams and ledges and otherrecesses within the booth, charged powder can adhere to booth interiorsurfaces.

In typical powder coating booth construction, an outer steel frameworkis provided for supporting individual panel members which form the roof,side and end walls of the booth. These panel members are known to bemade of a thermoformed plastic, such as polypropylene, polyvinylchloride (PVC), polyvinyl carbonate or polycarbonate. The floor may alsobe of thermoformed plastic or stainless steel construction. In otherknown embodiments, powder coating spray booths can have metallic walls,ceilings and vestibule ends, as well a metallic floor and exteriorsupport framework.

U.S. Pat. No. 5,833,751 to Tucker is an example of a powder coatingspray booth intended to reduce powder particle adhesion to the interiorsurfaces of the booth during an electrostatic powder spray operation.Tucker discloses a booth chamber comprising a pair of thermoformedplastic shells with smooth curvilinear interior surfaces that areintended to inhibit oversprayed powder particle adhesion. Two identicalends connect with the shells and an external support frame is disclosed,but not shown. Possible booth materials disclosed include polyvinylcarbonate and polycarbonate.

Known booth materials are available in limited sizes requiring somemethod of seaming to generate the overall size. These seams require mucheffort and cost to achieve a virtually uninterrupted, seamless surface.

In addition, known powder coating spray booths have numerous featuresthat reduce operational efficiencies. These suboptimal features areevidenced during powder coating color changes between successive runs ofdifferent coating colors and during assembly and maintenance of thebooth itself. Known powder coating spray booths use metallicexternal-support frames and stainless steel or thermoplastic, floors,walls and ceilings. During an electrostatic powder spray coatingoperation, oversprayed powder material can actually be attracted andadhere to these booth interior surfaces. Higher concentrations ofoversprayed powder coating material are typically seen in the immediatevicinity of the highly conductive steel frame members, which aretypically grounded or are somewhat insulated from ground and could actas capacitors. Although thermoformed plastics are typically thought ofas insulators, their insulative properties vary and powder particleadhesion can vary with the conductivity and resistivity of thesematerials. With age, conductivity of the thermoformed plastic materialscan increase with corresponding increases in powder particle adhesion,as they can absorb moisture from the ambient air over time. Ultravioletlight is also known to change the physical properties of thermoplasticsover time.

In addition, typical booths have numerous design features that act toincrease accumulated oversprayed powder coating materials in the spraybooth, thus increasing cleaning times during color change operations. Inbooths using panel members connected with each other and supported by anexternal frame, numerous seams exist throughout the booth interior thatentrap oversprayed powder coating material, thereby making the boothharder to clean during a color change or routine booth maintenance. Inaddition to the seams, ledges are present in some powder coating spraybooths on which spray gun application devices rest and are mounted, andwhere openings for doors and other access portals are reinforced andsecured, for example. These ledges can either extend into the booth or,more typically, extend away from the inner surface of the booth. Even ifotherwise angled or curved toward the floor from the typically verticalsidewalls, oversprayed powder coating material still tends to accumulatein these areas, thus making them more difficult to clean, as well.

In addition to the reduced spray booth operating efficiencies due topowder coating material adhesion as a result of electrostatics and boothdesign, booths constructed with frames and panel members and booths madeof thermoformed plastics increase assembly and maintenance times, thusfurther reducing operational efficiencies. Known booths require externalframes for structural support. Booths constructed of numerous individualwall and ceiling panel members must have their seams welded or otherwisesealed together. Installation of booths that require external frames forstructural support of any kind increase booth installation time. Boothshaving multiple panels forming the walls, ceiling and floors furtherincrease assembly time, and at best result in a semi-rigid enclosurethat falls short of a preferred robust containment envelope that issuitable for industrial environments.

Maintenance of thermoformed plastic booths is also a concern and has anegative impact on efficient booth operations. With thermoformed plasticbooth materials, workers and parts can accidentally nick and scratch thebooth internal surfaces rather easily. These surface imperfections anddiscontinuities are hard to clean areas and act to entrap powder coatingmaterial therein. In addition to increased cleaning times, maintenanceof the booth to remove the scratches and nicks are time-intensive atbest, and results of repair activities cannot restore a surface tooriginal condition. Both the ease at which thermoformed plastic boothscan be scratched and the time involved in repairing them makethermoformed plastic booths less than ideal as a powder coating boothmaterial.

It is desired, therefore, to provide a powder coating booth thatovercomes these and other shortcomings.

SUMMARY OF THE INVENTION

The invention herein provides for an improved powder coating spraybooth. In one embodiment, which is well-suited for retrofitting existingpowder coating spray booths, the invention herein comprises a pair ofopposed canopy halves that each have a sidewall and a ceiling portionthat can be connected to each other through a radius. This radius servesto reduce color change times and functions as a torsional supportelement for the wall and ceiling surfaces. Each canopy half is aseamless, composite, unitary structure that can connect with an existingbooth floor and with the existing booth vestibule and/or aperture end orends, and can be separated at the top providing for a narrow overheadconveyor slot opening typical in electrostatic powder coating spraybooths. The canopy halves are each self-supporting, which means they canbe assembled together with an existing floor and vestibule end or endsand no external frame is required to support the powder coating spraybooth of the present invention. By removing the external frame typicalof all known powder coating spray booths and constructing the inventivebooth canopies from nonconductive materials, the improved booth can beassembled much quicker and is more nonconductive to oversprayedelectrostatic powder particles. Thus, less oversprayed particle coatingmaterial adheres to the ceiling and walls of the inventive booth. Ofcourse, it can be appreciated by those skilled in the art that thisimproved embodiment of the invention can also work equally well with anew floor or vestibule end.

The canopy halves of the present invention are made from a number ofnon-conductive materials that are loaded onto a set-up tool having asmooth surface that has been prepared with a release agent. All thematerials can be non-metallic. Typical non-conductive layers can includea first, optional, sprayed on layer of gel-coat, which is anunreinforced resin layer that is allowed to set or cure. This firstlayer of the booth canopy halves serves as the booth interior surface.It may be pigmented, such as with white pigment, for aesthetics andfunctional reasons, such as to give a clean smooth appearance and tohelp the worker identify the location of oversprayed powder coatingmaterial within the spray booth during booth cleaning for a colorchange. The specific resin material chosen is non-conductive,ultraviolet light stable and impervious to moisture adsorption, evenover time. This layer can be followed by an optional layer of choppedstrand mat which is a random orientation glass fiber product. Alsoincluded are three necessary layers including a core having a suitablethickness to give the canopy halves structural rigidity and a first anda second layer of knitted glass fabric sandwiching the core forstrength. One or more handling tabs can be placed within the lay-up ofthe composite canopy halves, such as at perimeter edges or at the outerradius between the ceiling and wall portions, to assist with handlingthe composite canopy halves during lifting the newly formed canopy halffrom the tool, secondary operations in finishing the canopy half,storage, transportation and booth assembly at a production site. Thesehandling tabs can be simple nonconductive lugs, such as of similarcomposite construction and already cured before placement in the lay-up.

These layers are infused with a non-conductive resin and allowed tocure, thereby forming a composite structure that is strong, lightweight,nonconductive and can be repeatably reproduced on the same tool. Theinfusion and curing of the resin in the layered composite booth halvesare done under a bag that is sealed to the set-up tool and evacuated atroom temperature in a process that removes all voids and givesrepeatable results. One such process is known as Seeman Composites ResinInfusion Molding Process (“SCRIMP”). SCRIMP and improvements thereto arecovered in U.S. Pat. Nos. 4,902,215, 5,052,906 and 5,439,635, all toSeeman, hereby incorporated by reference in their entirety herein.

The cured canopy halves can be lifted off the set-up tool, trimmed andhave their access and other operational openings cut. A final exteriorlayer of gelcoat, again a pigmented or unpigmented unreinforced resinlayer can be applied for aesthetics and to further inhibit moistureadsorption over time and during shipping to the production site.Alternatively, an epoxy-based barrier coat can be applied in place ofthe gelcoat for the same purposes. Either coating layer on the partexterior serves to effectively seal the part from the elements duringshipping and fills in any pinholes that may be present on the exterioror trimmed surfaces of the composite canopy half.

In accordance with another aspect of the invention, each canopy half ofthe inventive spray booth can be essentially mirror images of each otherand produced with the same tooling. As such, they can be shipped to theproduction site in a nested configuration, minimizing shipping space. Inaddition, each canopy half can have one or more access and otheroperational openings which are positioned in the canopy half duringconstruction by measured placement of the core material, essentiallyremoving the core material where an access opening is desired. A flangearound the perimeters of the canopy halves can be provided by taperingthe core layer to zero thickness and creating a flange from theremaining layers, as described above. These perimeter flanges can beused for connecting the floor and the booth ends, which can be narrowedvestibules that are known to help retain oversprayed powder coatingmaterial inside the spray booth. Alternatively, one or both of thevestibule ends can be replaced with aperture bulkheads that establish apart opening in the booth end or ends.

Access openings can similarly have such perimeter flanges, to which canbe exteriorly or interiorly connected doors, application devicesupports, cyclone powder recovery units, and the like. Alternatively,man-door access openings and other operational openings, such as forautomatic gun slots and manual gun openings, can also be locatedthroughout the booth walls and not require the pre-established, measuredcore windows where the core material has been purposefully removed. Theman-door access and other operational openings can be created throughcut outs of the full-thickness composite, including the core materiallayer, with the resulting edges treated with a barrier coat duringsecondary operations, as described supra.

In another embodiment of the invention, each composite, seamless,unitary canopy half of the inventive booth comprises a ceiling portion,a sidewall and, additionally, a floor portion. The sidewall can connectto the ceiling and to the floor through respective radii. These canopyhalves are similarly constructed as described above on a suitable toolsurface and may also have one or more access openings and handling tabs.In addition, the floors of the respective canopy halves can each have adownwardly extending flange for connecting with the respective canopyhalf floor flange. Alternatively, the respective floor portions can beconnected via a bonded shiplap type of joint or a bonded spline jointusing a continuous glass fiber spline, for example. It will beappreciated by those of skill in the art that other joining methods maybe used without departing from the scope of the present invention. Inthis inventive booth embodiment, a utility base can be included whereinthe mated booth canopy halves can sit atop and may be connected thereto.Again, an existing or a new vestibule and/or aperture bulkhead end orends can connect to the perimeter flanges of the sidewall edges of thepresent embodiment. In this embodiment, only one centerline floor seamexists, versus the aforementioned embodiment which connects to aseparate floor, thus having two sidewall-to-floor seams that must besealed and prior to use.

In another embodiment of the invention, a method is disclosed forassembling a powder coating spray booth. The method includes providing apair of canopy halves that are each a seamless, nonconductive,self-supporting structure having a ceiling and a sidewall, andconnecting a perimeter edge of their respective sidewalls to a floor.The canopy halves can be non-metallic. Their composite constructionconsists of the nonconductive layers as described in the canopy halvesdescribed above. A vestibule or aperture bulkhead end can be connectedto either or both perimeter flanges of the sidewall edges of the each ofthe canopy halves. Assembly of such an inventive booth is less laborintensive than any known booth. No external frame is required to supportthe assembled booth.

In another embodiment, another method is provided for assembling anon-conductive powder coating spray booth. In this embodiment, the pairof canopy halves of the inventive method each comprise a ceiling,sidewall and floor portions. A utility base is provided and placed wheredesired. The respective canopy booth halves are connected to each otherat a respective floor edge flange, or other joint, and placed atop theutility base. The canopy halves can be connected to the utility base.The canopy halves can have respective perimeter edge flanges along eachof the common floor, sidewall, and ceiling edges and be connected to avestibule or aperture bulkhead end or ends at either or both of therespective perimeter edge flanges. The canopy halves can besubstantially nonconductive. The utility base can be made of carbonsteel.

In another inventive powder coating booth embodiment, a nonconductive,self-supporting, spray booth canopy is provided that includes a pair ofcomposite canopy halves each having a wall and ceiling portion and atleast one integral vestibule end half, or aperture bulkhead half. Inaddition, each canopy half can have an integral floor portion with theassembled canopy halves requiring a suitable utility base section forconnecting thereto. The integral floor portions of either half, or bothhalves may be sloped to facilitate oversprayed powder coating materialcollection in one or more collection troughs located below the boothfloor. Otherwise, a floor is provided to connect with the canopy halvesat perimeter wall and vestibule or aperture bulked edges. An overheadconveyor slot opening for passing parts through the booth can beprovided. The canopy halves are nonconductive for mininizing theadherence of electrostatically charged oversprayed powder coatingmaterial to the booth interior surfaces.

Various other embodiments of the invention are described and claimedherein, and other features and advantages of the present device willbecome apparent from the following detailed description, with referenceto the accompanying drawings and claims, which form a part of thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of the present inventionwith aperture bulkhead ends.

FIG. 1A is an enlarged view of section A in FIG. 1 depicting acore-edge, full thickness operational opening.

FIG. 1B is a partial view like that of FIG. 1, with the aperturebulkhead end replaced with a vestibule end.

FIG. 2 is an exploded perspective view of an alternative embodiment ofthe present invention depicting one each aperture bulkhead and vestibuleends.

FIG. 3 is side view of a canopy half of FIG. 1 depicting typical solidedge, flanged access and operational openings.

FIG. 4 is a side view of the canopy half of FIG. 1 opposed to the canopyhalf of FIG. 3, shown with sidewall edge cutouts for connecting with acyclone powder collection system, and similarly depicting solid edgeoperational openings.

FIG. 5 is an end view of the canopy half of FIG. 3.

FIG. 5A is an enlarged view of Section A in FIG. 3.

FIG. 5B is an enlarged view of Section B in FIG. 3.

FIG. 6 is an end view of a canopy half of FIG. 2.

FIG. 6A is an enlarged view of Section A in FIG. 6.

FIG. 6B is an enlarged view of an alternate joint for the joint depictedin FIG. 6A.

FIG. 6C is an enlarged view of yet another alternate joint for thatdepicted in FIG. 6A.

FIG. 6D is an enlarged view of Section D in FIG. 6.

FIG. 6E is an enlarged view of an alternate longitudinal stiffener jointfor that depicted in FIG. 6D

FIG. 7 is a perspective view of a set-up tool used to make the compositecanopy halves of the spray booth of the present invention, as depictedin the embodiment of FIG. 1.

FIG. 8 is a side view of an alternative set-up tool that can be used tomake canopy halves as shown in FIG. 2, for the present invention.

FIG. 9 is a perspective view of an alternative embodiment of the presentinvention.

DETAILED DESCRIPTION

Referring now to the figures, which are for purposes of illustrating thepresent invention and not for limiting same, FIG. 1 depicts a powdercoating spray booth, or containment structure, according to the presentinvention at 10. The booth 10 is shown including a first and secondcanopy half, 12, 14, respectively. The canopy halves of this inventiveembodiment for booth 10 are best shown in FIGS. 1, and 3 through 5. Eachcanopy half 12, 14 is a unitary, seamless self-supporting, compositestructure. It is self-supporting in the sense that it is structural andof sufficient strength, that when assembled into the inventive spraybooth, an exterior frame is not required for structural support, as inknown powder coating spray booths. A single, continuous conveyor slotopening 34 is maintained at the top center of booth 10, as shown, forconveying grounded parts through the booth to be electrostatically spraycoated therein, for example.

In the present inventive embodiment, each canopy half 12 is a mirrorimage of respective canopy half 14, except for the location ofoperational and access openings 11, 11′, 11″ for doors for automatic andmanual spray application devices (not shown) and worker access to thebooth and the like, and the optional cutouts 13 at an edge of perimetersidewall 16 for a cyclone powder collection system, for example (notshown). As such, each canopy half 12, 14 can be made on the same tool,such as tool 50 (FIG. 7). Each canopy half 12, 14 has a sidewall 16 andan integral ceiling portion 18 connected to each other through a radius17. Radius 17 serves to reduce color change times and functions as atorsional support element for the wall and ceiling surfaces. Each canopyhalf is a unitary, seamless, self-supporting, composite structure, thelayers of which are best shown in FIGS. 5A and 5B.

Each canopy half 12, 14 is a seamless, self-supporting, compositestructure, comprising at least three, nonconductive layers. A corematerial layer 26 is sandwiched between a first bi-directional glassfabric layer 24 and a second layer of bi-directional glass fabric 24. Aninfusion resin, or gelcoat, is drawn by vacuum throughout the composite,thereby binding together layers, 24, 26 and second layer 24, when cured,thus forming the composite canopy half 12, 14. An optional unreinforcedresin, or gelcoat, layer 20, preferably of the same type as the infusionresin can serve to form the interior surface 15 of the spray booth 10,instead of the resin-infused first inner layer of bi-directional glassfabric 24. The unreinforced resin layer could be pigmented, such as withwhite pigment for aesthetic and functional reasons, to aid indetermining where oversprayed powder coating material may be adheredduring color change operations. An optional layer of chopped strand mat22 can be positioned in the lay-up between the unreinforced resin layer20 and the first layer of bi-directional glass fabric 24. The layers arechosen for their nonconductive properties and are chosen based onprocessing and material cost considerations. Each layer and the infusionresin are preferably completely non-metallic. A price-competitive,structurally self-supporting, non-conductive spray booth 10, comprisinga pair of opposed seamless canopy halves 12, 14 is the result. As such,the tendency of charged powder particles to stick to booth interiorsurfaces is substantially reduced in electrostatic powder sprayapplications. It will be appreciated by those of skill in the art thatsubstitutes may be available for each of the preferred material layers,so long as each canopy half is a non-conductive, composite structurethat is seamless and does not require an outer framework for structuralsupport. Again a known process that can be used for the room temperatureresin infusion and curing operation is known as SCRIMP, and is referredto above.

In forming the composite canopy halves 12, 14 using the resin infusionprocess, the layers 20, 22, 24, 26 and 24 are assembled on a tool, suchas set-up tool 50 shown in FIG. 7. Set-up tool 50 itself can be ofcomposite construction comprising steel reinforcement and balsa woodcoring construction for stability. Tool 50 should be of sufficientstiffness and strength to allow workers to walk upon it while loadingthe tool and be durable enough such that it is a reusable tool capableof lasting for the construction of numerous canopy halves 12, 14. Tool50 can be of any sufficient length L and width W, and preferably largeenough for the largest expected booth canopy half dimensions, which maybe upwards of thirty feet L by twelve feet W, or even larger. In thissense, tool 50 is reusable and expandable, or universal, to constructcanopy halves of various dimensions fitting within the limitations of Land W. In addition, multiple tools 50 can be laid end-to-end (not shown)to create even longer L dimensioned canopies 12, 14. In such instances,the tools 50 can be edge joined with bolts, e.g., and the resultant toolseam can be dressed with a tooling wax (joined tool 50 configuration notshown). Furthermore, tool 50 walls spanning the length L and width W caneach be further expanded with an increased wall portion (not shown, butsimilar to alternate tool 54 shown in FIG. 8 and described below—andedge-joined as described above). Tool 50 surface 52 is finessed to asmooth finish. Materials for each canopy half are loaded onto surface 52and built from the booth interior surface 15 outward. Each canopy half12, 14 can be constructed on tool 50 as described below.

The first step in constructing the seamless composite canopy halves 12,14 is to apply a release agent to smooth tool surface 52. The releaseagent is preferably a silicone-free release agent to ensure part releasefrom the tool 50.

Next, and in a preferred embodiment, the optional unreinforced resinlayer 20 is applied, such as by a spray application device, to surface52 and allowed to set or cure. This resin forms the unreinforced resin,or gelcoat, layer 20, the innermost surface of which that is contactingtool surface 52 forms booth interior surface 15 of canopy halves 12, 14.This layer 20 may be of any suitable thickness, such as from about 0.01inches to about 0.1 inches, or even greater, but preferably from about0.025 inches to 0.035 inches thick to provide a durable lightweightsurface layer. The gelcoat, or unreinforced resin, layer 20 can bepigmented, such as with white pigment, for aesthetic and functionalreasons. The smooth hard white surface is easier for workers to seeoversprayed powder that is adhering to booth interior canopy surfaces 15and must be cleaned during a color change operation. Gelcoat layer 20forms a durable interior surface that is impervious to moistureadsorption and does not degrade over time or due to ultraviolet light.In addition, it is impact and scratch resistant and scratches that doform can be easily buffed out. Suitable resins for gelcoat layer 20 inthis electrostatic environment are those that cure into nonconductive,resilient, moisture impervious layers, such as an epoxy-based resinsystem or a vinyl ester resin system. Derakane 441-400 from DowCorporation, and CoREZYN VEX 169-540, from Interplastic Corp. of St.Paul, Minn., are exemplary of suitable vinyl ester resins for thispurpose.

An optional, but preferred second layer 22 comprises chopped strand mat.Chopped strand mat is a well-known random orientation glass fibercomposition. Although a commodity product with various weight densitiesand manufacturers, a 1.5 ounce E-glass chopped strand mat from OwensCorning is sufficient for these purposes and is substantiallynon-conductive. The chopped strand mat layer 22 has both aesthetic andfunctional purposes. The chopped strand mat layer 22 serves as a veilthereby preventing the next layer 24, which is bi-directional glassfabric, from showing through the unreinforced resin, or gelcoat, layer20 in what is commonly referred to in the art as “print-through.” Thechopped strand mat reduces the possibility of print-through. Inaddition, by spraying the chopped strand mat layer 22 on wetted with theinfusion resin, a more durable surface is created. The infusion resin ispreferably the same as that forming layer 20, but may be slightly moreviscous, depending on the styrene content. Such a surface can be walkedupon by workers, preferably wearing protective booties or overboots,when loading the remaining layers 24 and 26. The chopped strand matlayer 22 will take up shear and torsional loads such as that applied bya worker's foot when turning, thereby preventing defects to theunreinforced resin layer 20 underneath, such as lifting off of theunreinforced resin layer from the tool surface 52 under such shear andtorsional loads.

Next, workers apply a first layer 24 of knitted bidirectional glassfabric that adds strength to the composite when cured. As mentionedabove, the workers can walk upon the partial lay-up when applying thelayer 24 of bi-directional glass fabric, or they can be suspended abovethe surface or access the surface by properly placed scaffolding (notshown). A suitable material choice and weight is CM 3610 knittedbi-directional E-glass. This is a nonconductive commodity product withvarious manufacturers. Brunswick Technologies Inc. is one such suitablemanufacturer. It is appreciated that other weights of knitted or wovenreinforced glass fabrics of varying mesh sizes may be equally suitablefor this structurally reinforcing, yet non-conductive layer 24.

Next, workers load the core material layer 26. Again, the materialchosen must be nonconductive and possess appropriate physical propertiesto ensure structural rigidity. A suitable core material for this purposehas been found to be the family of semirigid, closed cell, polyvinylchloride (PVC) foams. Again, these are non-conductive commodityproducts. Baltek Corporation's AirLite™ B-6.25 in one inch thickness hasbeen found suitable for this purpose. This foam has a density of 6.25pounds per cubic foot Denser foams may be used throughout the compositestructure, or at key locations, such as for the floor portions 19 (seeFIGS. 2 and 6) or near the operational and access openings 11, 11′, 11″.Of course it will be appreciated by those of skill in the art that anynumber of other closed cell foams or other nonconductive core materialsmay work for this specific electrostatic application. In addition,varying thicknesses and core material densities may also work equallywell for this nonconductive usage. The foam core material can havespaced holes for the resin to timely flow through during the infusionprocess, as described above. These holes can preferably be mechanicallyplaced perforations in a desired spacing and pattern. Suitableperforation spacing will vary based on the foam thickness and theviscosity of the infusion resin, for example. One eighth inch diameterperforations spaced on two inch centers in an echelon grid pattern issufficient for these purposes.

During the core material placement, or loading of the core materiallayer 26, by the workers, operational and access openings 11, 11′, 11″for doors, automatic and manual spray application devices, worker accessto the booth and the like are placed and determined by removing the foamlayer in these areas. Preferably, the operational and access openings11, 11′, 11″ will have perimeter edge flanges 21 defining the openingsin the canopy halves 12, 14. These edge flanges 21 may be formed bytapering the foam core material layer 26 to zero thickness from its fullthickness, through a taper, such as a forty-five degree taper, forexample. As such, there will be a transition region, or zone, in thefinished composite canopy halves 12, 14, wherever the foam corethickness tapers from full thickness to zero thickness at a firstinboard edge of a flange 21, 21′, 21″. The flanges, therefore, aretypically composed of all layers excepting the core material layer 26,comprising namely, an unreinforced resin layer 20, a layer of choppedstrand mat 22, and two layers of bi-directional glass fabric 24, all ofwhich are bound together with a resin into a composite structure that isintegral with the canopy halves 12, 14. See FIGS. 5A and 5B.Alternatively, the flanges 21 around the operational and access openings11, 11′, 11″ can be omitted. Operational and access openings 11, 11′,11″ can be made using the 6.25 pounds per cubic foot, or higher density,foam all the way to the edges of the desired openings 11, 11′, 11 ″thereby reducing production time by eliminating the layout and cuttingof the core material 26 during tool loading. The openings 11, 11′, 11″would be cut in secondary operations and the cut edges treated with abarrier coating 28 (FIG. 1A), for example, as described below.

FIG. 5A shows edge flanges 21 that are also typical of edge flanges 21′for connecting the composite canopy halves 12, 14 to the floor 30 at thebottom 23 of sidewalls 16, or the edge flanges 21″ that are forconnecting to a vestibule end 32 at edges 25 of sidewalls 16 and ceilingportions 18. In addition, the flanges 21 shown at FIG. 5A are typicalfor perimeter flanges 21 found around the operational and accessopenings 11, 11′, 11″ and for optional cyclone openings 13.

FIG. 5B shows a flange 31 that is a ninety degree flange. Flange 31 isat the peripheral edge of the ceiling portion 18 of each canopy half 12,14 and the upstanding leg of flange 31 serves to define the conveyorslot opening 34 in the assembled booth 10. Functionally, the opposedpair of flanges 31 serve as a bumper guard for the conveyor, therebypreventing damage to the canopy halves 12, 14 by parts or conveyor hooks(see 70 and 62 in FIG. 9, for example) for attaching to parts that mayaccidentally sway and contact the canopy halves 12, 14.

After the foam core layer 26 with associated perimeter flanges 21, 21′,21″ and 31 are in place, a second layer of bi-directional glass fabric24 is laid over top of the foam layer 26 and associated flanges 21, 21′,21″ and 31. Again, this layer can be identical to the first layer 24 ofbidirectional glass fabric and serves to strengthen and give structuralrigidity to the finished composite canopy halves 12, 14. It should benoted that optional hard points, or handling lugs or tabs 60, preferablyin the form of nonconductive, already cured composite construction, canbe placed in the lay-up where desired, prior to this second layer ofbi-directional glass fabric 24 being applied. These handling lugs ortabs 60 are shown on canopy half 12′in FIG. 2, and may be placed wheredesired in the lay-up, thereby forming a part of the. compositestructure therewith to assist with later handling, transportation andset-up of the pairs of canopy halves 12, 14, 12′, 14′ (FIG. 2) and 12″,14″ (FIG. 9). Preferably, two or more handling tabs 60 are placed on thecanopy half (as on 12′ in FIG. 2) near the center of gravity of thecanopy half such that the canopy half is held with the sidewall 16, 16′substantially vertical to assist with installation to the floor 30(FIG. 1) or the opposed canopy half 14′ and utility base 40 (FIG. 2).

The SCRIMP process, already incorporated by reference, supra, via U.S.Pat. Nos. 4,902,215, 5,052,906 and 5,439,635, all to Seeman, or anotherresin-infusion process, is now applied to the lay-up. Briefly stated, alayer of disposable porous plastic peel-ply is placed over top thelay-up and loaded tool 50. This is followed by laying resin distributionmedia and delivery lines, which are connected to a resin source, asdesired over the peel ply. A vacuum is connected by a line or lines thattypically extend so that they pull a vacuum near the peripheral edge, oredges of the canopy half 12, 14 lay-up. A plastic or mylar bag, or sheet(not shown), is laid over this entire lay-up and sealed to the tool 50,such as by using double-back Tacky Tape® from Schnee-Morehead Inc. Theresin distribution lines and vacuum lines that must extend under themylar sheet are first wrapped with the Tacky Tape® which is then securedto the sheet and the tool 50 (not shown).

Next the sealed bag and loaded tool 50 are evacuated via a vacuum pump(not shown). The vacuum can be checked by timing the evacuation andturning the vacuum pump off to see if the vacuum is lost. If a good sealis in place, the vacuum pump is turned back on and the infusion resin isallowed to be drawn into the resin distribution lines and media, throughthe peel ply and through the entire lay-up on loaded tool 50. Theinfusion resin is drawn through the lay-up and fills all voids,including through the perforations in core layer 26, both layers ofbi-directional glass fabric 24 and the optional chopped strand mat layer22 all the way to the optional cured unreinforced resin layer 20. Asnature abhors a vacuum, the infusion process occurs rather swiftly.Typically, the vacuum may be drawn to about twenty-seven inches ofMercury. It takes about twenty-five to thirty minutes for the infusionresin to fill a 250 square foot part by occupying all voids in thereinforcement products and coring and another twelve hours to cure atroom temperature. No autoclave is required. Obviously, resin infusionand curing time depends on the part size and thickness and ambient orroom temperature. The vacuum is maintained throughout this time.

Once the resin is cured, the resin and vacuum lines are detached, thepeel ply and resin distribution lines and media are removed and disposedof. The partially finished canopy half 12 or 14 is lifted off tool 50,such as by a simple overhead crane (not shown) connecting to handlingtabs 60, for secondary operations. Secondary operations include trimmingperimeter edges and cutting out operational and access openings 11, 11′,11″ while leaving the desired flanges 21 surrounding them. This can beaccomplished preferably using a template that is suction clamped to thefinished interior surface 15 of unreinforced resin layer 20 and using amanual or automatic router cut out the composite around the inside ofthe template (not shown). Alternatively, and as mentioned above,operational and access openings 11, 11′, 11″ can be cut from the fullthickness composite including the core material layer 26, as shown inFIGS. 1 and 1A, leaving an exposed core edge for the operational oraccess openings 11, 11′, 11″ that would be treated with a barriercoating 28 in secondary operations. In addition, optional cutouts 13 atan edge of perimeter sidewall 16 for a cyclone powder collection systemcan be trimmed open, thereby leaving corresponding solid edge flange21″. If desired, it should be noted that within one or more of theoperational and access openings 11, 11′, 11″, such as the large accessdoor 11″ for worker entry into the booth, a destructive test sample orsamples can be made by simple placement of all layers 20, 22, 24, 26 andsecond layer 24, over a section of the eventual access opening 11″during lay-up, which would be resin-infused and cured with the boothhalf 12 or 14. When the access door opening 11″ is routed out insecondary operations as herein described, the test article can befurther trimmed and destructively tested for sufficiency of bonding,mechanical properties, electrostatic properties and general qualitycontrol, for example.

As a final step in secondary operations prior to readying for shipment,an exterior barrier coat layer 28 is applied. Barrier layer 28 can beeither a layer of epoxy-based, nonconductive barrier coat, or a layer ofnonconductive unreinforced resin, similar to, or the same as, that oflayer 20. This will fill any possible pin holes that may be exposedthrough the cured resin-infused outer layer 24 of bi-directional fabricand creates a further moisture impervious layer serving to furtherprevent moisture intrusion to the composite. In either case, the barriercoat 28 will typically be thinner than layer 20, such as having athickness on the order of from about 0.003 to about 0.009 inches, in apreferred example. In addition, it may be pigmented white foraesthetics, since it serves to form the outer layer of the booth canopyhalves 12, 14. The outer barrier coat 28 also serves to seal all trimmededges, including those of all perimeter flanges 21, 21′, 21″ and 31.

An inventive method of assembly of powder spray booth 10 is hereinprovided. The method of assembly is straightforward and lesstime-consuming than assembly for any known powder coating spray booths.Workers simply unload the canopy halves 12, 14, each having a ceilingportion 18 and an integral sidewall portion 16, hold them in place abovean existing floor, or a new floor, 30 and attach the lower flanges 21′of each canopy half 12, 14 to the floor assembly 30, such as with boltsthrough corresponding holes spaced along the flanges 21′ and the floorassembly 30. Next, a vestibule end 32, which again can be eitherexisting, such as in a retrofit assembly, or new, is connected similarlywith bolts (not shown) to edge flanges 21″ around the sidewalls 16 andceiling portions 18 of respective canopy halves 12, 14 and to floorassembly 30. An optional second vestibule end 32 can be similarlyconnected to the opposite perimeter edge of canopy halves 12, 14. Again,corresponding holes in the perimeter flanges 21″ of respective ceilingportions 18 and sidewalls 16 of canopy halves 12, 14 would be bolted toholes in the vestibule end 32. Assembly bolts may be non-conductiveglass-reinforced plastic bolts or steel. Assembly seams exposed to thebooth 10 interior could be sealed, as is known in the art. No exteriorframework is necessary for booth 10, since the composite canopy halves12, 14 are structurally self-supporting, that is, they are strong enoughto hold their own weight and are able to support application devices(not shown) within, or attached to, operational openings 11, 11′, forexample.

An alternative embodiment of the inventive spray booth 10′ is shown inFIGS. 2, 6, 6A and 6B. The same reference numbers will be used for booth10′ where appropriate and where similar structure is depicted fromsimilarly referenced items in booth 10 of FIGS. 1, and 3-5. As such,booth 10′ comprises two one-piece composite canopy halves 12′, 14′, eachcomprising a ceiling portion 18, a sidewall portion 16′ and a floorportion 19. A single, continuous conveyor slot opening 34 is similarlymaintained at the top center of booth 10′, as shown, for conveyinggrounded parts through the booth to be spray coated therein, such as byone or more electrostatic spray application devices (not shown). Canopyhalves 12′, 14′ are constructed similarly to canopy halves 12, 14, asdetailed above. They comprise the same materials and layers, namelyoptional layers 20 and 22 and first and second layers 24 sandwichingcore material layer 26, as well as optional barrier coat layer 28applied in secondary operations off the production tool 54 (FIG. 8).Layer 20 can similarly serve as the interior surface 15′ of booth 10′.Again, canopy halves 12′, 14′ can have one or more optional hard points,or handling lugs or tabs 60, preferably of nonconductive, already curedcomposite construction, that can be placed in the lay-up where desired.The canopy halves 12′, 14′ are similarly one-piece and seamless and ofnonconductive and, preferably non-metallic, composite construction.

Referring now to FIGS. 6, 6D and 6E, a utility base section 40 that canbe fitted with a floor sweeper mechanism, process air, electricalservices and other process requirements (not shown) is provided for theassembled canopy halves 12′, 14′ to be supported atop. Each canopy half12′, 14′ can have a longitudinal beam 42, 42′ connected to an undersideof their respective floor portions 19, either attached exteriorly, suchas with epoxy, or the longitudinal beams 42, 42′ can be integral withthe floor portions 19, as shown in FIGS. 6D and 6E. As illustrated,longitudinal beams 42, 42′ are placed in the lay-up, as described supra,prior to the SCRIMP or other resin infusion process and curing. Thelongitudinal beams can be placed in the lay-up directly atop the corematerial layer 26 and before and under the second layer of bidirectionalglass fabric 24. The longitudinal beams offer strength and structuralrigidity and may be comprised of any suitable material, such as highdensity foam (FIG. 6D), glass fiber reinforced foam or a pultruded glasshollow box beam section 42′ (FIG. 6E). Aligned holes 43 in the utilitybase 40 and 44 in the longitudinal beams 42, 42′ can be secured togetherwith a standard bolted connection. Bolt holes 44 in the beams 42, 42′could be drilled during installation to match corresponding pre-drilledholes 43 in utility base 40 that can be spaced along the length ofutility base 40.

The floor portions 19 are integral with the canopy halves 12′, 14′ forthis inventive booth 10 embodiment. Therefore, there is only one floorseam instead of two, as was required in booth 10 to connect eachsidewall 16 to the floor 30. The respective floor portions 19 of canopyhalves 12′, 14′ each additionally have a ninety degree, downwardlyextending mating flange 36 (see FIG. 6A) that is similar to flange 31,as described supra. These flanges are created by the lay-up of materiallayers 20, 22, and two layers of 24 around comer 58 on floor moldsection 57. The opposed mating flanges 36 of canopy halves 12′, 14′ areconnected together for the assembled booth 10′, such as by boltedconnections through corresponding holes along the respective flanges 36(see FIG. 6A). Alternatively and not shown, opposed mating flanges 36could be bonded or clamped to each other. For example, to further reducethe floor seam 39, a bonded shiplap type of joint could be established(FIG. 6B) or a bonded continuous glass fiber (G-10) spline joint (FIG.6C) could be used to connect the respective floor portions 19 of canopyhalves 12′, 14′. Either of these alternative joints can be preparedduring secondary operations. It will be appreciated by those of skill inthe art that other joints known in the mechanical and structural artsmay be equally suitable and it is intended that these are within thescope of this disclosure as well. Additionally, at the booth ends a pairof vestibule ends 32 or aperture bulkheads 33 can connect with perimeterflanges 21″ that are at the respective canopy half 12′, 14′ edges, as atceiling portions 18, sidewalls 16 and floor portions 19. Of course, itwill be appreciated that one canopy end can be a vestibule end 32,whereas the opposite end can consist of an aperture bulkhead 33. Withintegral floor portions 19 connected to sidewalls 16 through a radius 38and only one seam connecting composite canopy halves 12′, 14′, as atopposed flanges 36 connected with bolts 37 (FIG. 6A), there is lessoversprayed powder particle adhesion to surface 15′ in electrostaticcoating operations. Using such a singular floor joint, the time to cleanbooth 10′ during a color change operation is significantly reduced.

Since canopy halves 12′, 14′ additionally have floor portions 19integral to each of them, wherein floor portions 19 can be connected tothe respective sidewalls 16 through a radius 38, a different set-up toolmust be used. Referring now to FIG. 8, set-up tool 54 can be used toload, infuse and cure canopy halves 12′, 14′ using the SCRIMP or otherresin-infusion process. Set-up tool 54 has widths W, W″ and a length Las shown, and comprises a roof mold section 55, a wall mold section 56,and a floor mold section 57. Width W′ is slightly greater than the widthW′ such that the booth halves 12′, 14′, when assembled into booth 10′,will include conveyor slot 34. Conveyor slot 34 can be on the order offour inches, or so, and is typical of conveyor slot openings known inpowder coating spray booths. As such, W′ can be about two inches greaterthan W″, for example. Since the mold sections 55, 56, 57 are connectedtogether, such as by bolting them (details not shown), the resultingseam s, or joints, between mold sections should be dressed, such as witha tooling wax as is known in the art.

Tool 54 can be made expandable by using wall sections of varyinglengths, to change the overall length L. Similarly, tool 54 can beexpandable for either or both widths W′ and W″ by connecting an optionalexpander section 59 to the roof mold section 55 and floor mold section57 of tool 54 as desired. Expander sections 59 can be bolted, as atsurfaces 51 and 53, with the resulting joint or seam treated withtooling wax prior to use. Obviously, it will be appreciated that avariety of differently sized expander sections 59 would allow numerouswidths W′ and W″ for canopy sections 12′, 14′.

A method for assembling a powder coating spray booth 10′ is alsoprovided. The method has few steps and assembly time is much less thanconventional, exterior frame-supported spray booths. A utility base 40is provided and placed where desired. The pair of nonconductive,preferably non-metallic, self-supporting, composite canopy halves 12′,14′ are provided at the assembly site. The canopy halves 12′, 14′ areconnected together, such as at the perimeter floor edge flanges 36 withbolts 37 (FIG. 6A), and the assembly is placed atop the utility base 40.The utility base can be connected to the assembled canopy halves 12′,14′ such as with bolts 44 through corresponding holes 43, 44 in theutility base 40 and the support beams 42 of the canopy halves 12′, 14′,respectively (FIGS. 6D, 6E). One or a pair of either vestibule ends 32or aperture bulkheads 33, or one each vestibule end 32 and aperturebulkhead 33 per respective booth 10′ end, can be provided and connectedto respective perimeter edge flanges 21″ of the ceiling portions 18, thesidewalls 16 and the floor portions 19 of each of the canopy halves 12′,14′.

An alternative embodiment for the inventive spray booth 10″ isillustrated in FIG. 9. Booth 10″ comprises canopy halves 12″, 14″ eachcomprising integral ceiling portions 18″, sidewalls 16″ and floorportions (not shown, but similar to 19 in FIG. 2) and each furtherincluding an integral portion of either or both end units. The end unitscan be either aperture bulkhead ends (such as 33 in FIG. 1) or vestibuletype end units 32′ (shown with both ends being vestibule type end units32′). Of course, one end can be a vestibule type end unit 32′ whereasthe opposed end unit can be an aperture bullhead (such as 33 in FIG. 1).A different tool (not shown) with corresponding mold surface would berequired. This could further minimize the conductivity and assembly timeof the resulting electrostatic powder coating spray booth 10″. Booth 10″could be made with the same materials and layers using the SCRIMP orother resin-infusion process, as described above for canopy halves 12,14, 12′ and 14′, and is structurally self-supporting, non-conductive,and preferably, completely non-metallic. Since there are is only oneseam, oversprayed electrostatically charged powder particle adhesion tothe interior booth canopy surfaces is substantially reduced. Booth 10″can have one or more operational and access openings 11, 11′, 11″ suchas for automatic or manual electrostatic spray gun openings 11, 11′ anda service door 11″ for worker entry into the booth 10″. A conveyor slotopening 34′ can be provided for conveying parts 70 through the booth 10″to be spray coated therein. The overhead conveyor 62 can have partholders 64, as is known in the art. Canopy halves 12″, 14″ could beconnected together, such as with bolted connections (not shown), andfurther bolted (not shown) to a utility base 40′.

The invention has been described herein with reference to the preferredembodiments. Obviously, modifications and alterations will occur toothers upon a reading and understanding of this specification. It isintended to include all such modifications and alterations insofar asthey come within the scope of the appended claims or the equivalentsthereof.

1-27. (Canceled)
 28. A method of assembling a powder coating spray boothdefining a chamber for powder spray coating articles therein, comprisingthe steps of: a) providing a floor and a pair of nonconductive,self-supporting, composite canopy halves each having a ceiling portionand an integral sidewall; and b) connecting the floor with a lowerperimeter sidewall edge of each of the respective canopy halves.
 29. Themethod of claim 28, wherein the composite canopy halves each comprisethe following nonconductive, non-metallic layers bound together with anon-conductive, non-metallic resin: a layer of unreinforced resin, whichforms a surface exposed to the inside of the chamber; a layer of closedcell polyvinyl chloride foam core material; a first and second layer ofbi-directional glass fabric, the first layer between the unreinforcedresin layer and the foam core layer and the second layer on the oppositeside of the foam core layer from the first layer.
 30. The method ofclaim 28 further comprising the steps of providing a vestibule end andconnecting the vestibule end to a respective perimeter edge of each ofthe canopy halves.
 31. A method of assembling a powder coating spraybooth, comprising the steps of: a) providing a utility base, and a pairof nonconductive, self-supporting, composite canopy halves, each canopyhalf comprising integral ceiling, sidewall and floor portions; b)placing the utility base in desired location; and c) connecting thecanopy halves together at the respective edges of the floor portions;and d) placing the connected canopy halves atop the utility base. 32.The method of claim 31 further comprising the step of connecting theutility base with each of the canopy halves.
 33. The method of claim 31further comprising the steps of providing a vestibule end and connectingthe vestibule end to a respective perimeter edge of the ceiling, thesidewall and the floor portions of each of the canopy halves.
 34. Themethod of claim 31 wherein the composite canopy halves each comprise alayer of non-conductive, unreinforced resin that serves as the interiorsurface of the canopy halves, a layer of core material, a first andsecond layer of bi-directional glass fabric, one layer on each side ofthe core material layer, and resin for binding all the layers together.35. The method of claim 34 wherein the canopy halves each furthercomprise a layer of chopped strand mat interposed between theunreinforced resin layer and the first layer of bi-directional glassfabric and bonded thereto with the resin.
 36. A powder coating spraybooth for spraying powder coatings on an article inside the booth andfor containing oversprayed powder coating particles therein, comprisinga pair of non-metallic, self-supporting, composite, seamless canopyhalves for enclosing a powder coating booth chamber, each canopy halfhaving an integral ceiling portion, wall portion, floor portion and anend unit portion, the canopy halves being connected at respective floorportion edges and connected to a utility base, wherein at least one ofthe canopy halves has at least one opening in the wall of at least oneof the canopy halves.
 37. The powder coating spray booth of claim 36wherein the canopy further comprises an overhead conveyor slot openingfor conveying parts through the booth to be powder spray coated therein.38. The powder coating spray booth of claim 36 wherein the booth is usedfor electrostatic powder spray coating and wherein the canopy halves arenon-conductive for minimizing the likelihood of adherence of theoversprayed powder particles to any interior surfaces of the canopyhalves.
 39. The powder coating booth of claim 36 further comprising avestibule end, wherein the vestibule end is connected to a respectiveperimeter edge each of the canopy halves.